Minimization of brine impacts on seabed biodiversity, with special reference to Cymodocea nodosa meadows.

Project is financed by the Ministry of Environment, Rural and Marine Affairs (cod: 0056/SGTB/2007/2.4).

Water desalination is currently the main technology used to meet the requirement in fresh water, widely used throughout the world, especially in arid countries such as Saudi Arabia, the United Arab Emirates, the United States and also Europe.

In Spain, desalination technology has been used since the 1970s, initially in the Canary Islands spreading later on to the Balearic Islands, the Iberian Peninsula, Ceuta and lately Melilla. Nowadays, freshwater production reaches approximately 1,200,000 m3/day: 700,000 m3/day of seawater desalination and the remaining refers to brackish water.

Among the processes that exist in desalination technology, reverse osmosis is most commonly used, due to its higher efficiency and relatively low cost of drinking water production (Morton, Callister& Wade, 1996; Einav et al. 2002; Purnama, Al-Barwani& Al-Lawatia, 2003). This process is based on the principle that every saline solution has an osmotic pressure proportional to the concentration of salts. If a semipermeable membrane is placed between two solutions with different ion concentrations and osmotic pressure, this difference will produce the flow of solvent (and a minimal part of the solute) from less to more concentrated solution. In the case of reverse osmosis, an applied external pressure overcomes the difference in osmotic pressure and results in an opposite direction of a solvent flow is (Einav et al, 2002). As a result, a hypersaline or brine water is produced which is further discharged into the sea.

The main objective is to establish the carrying capacity of subtidal soft bottoms, affected by desalination water rejection, with special reference to the threshold of Cymodocea nodosa meadows. Here we aim to establish the maximum value of brine discharge tolerable by a particular coastal ecosystem. The degree of discharge affection on the marine environment is crucial for future deployment of desalination plants in the Canarian coasts and for elimination of negative effects of those which are presently operated. It is thus intended to develop methodology for study, conservation and control of Cymodocea nodosa meadows, which is a unique marine ecosystem that serves as a breeding and refuge area for countless species of economic and geologic interest.